Time compressing video content involves making the video content presentable to the viewer in a timescale that is different from the timescale of the original video content. Automatic time compression of video content is useful in a variety of different situations, for example to fit thirty second television commercials into twenty-eight seconds available for addressable commercials, or more generally to fit video content into smaller intervals to create room for visual effects.
Traditional compression, whether based in audio or video, includes removing small bits of information that will be undetectable to a viewer's eye or listener's ear. In an audio context, information and data relating to frequencies inaudible by the human ear may be removed to shrink the size of the audio file. When the audio is replayed, a typical listener does not notice the missing frequencies because she would not have been able to detect it even if it were still there.
The removal of information from a video stream presents unique problems. Time compressing a video traditionally involves removing pieces or video from a sequence in order to shorten the length to a desired length. Time-compression of video is difficult because of the high sensitivity of the human eye and its ability to notice the smallest discrepancies or discontinuities in a video sequence. Even if the viewer is unaware of the removal of some parts of the video, the video may still blur, become choppy, or contain visible static. When watching time-compressed video, the quality of the viewer experience is dependent on the minimized discontinuities in the viewer-perceived flow of time, which depends on the extent of displacement of visible objects in either their three-dimensional position or in their color space. The more drastic the displacement, the higher the level of viewer-perceived discontinuity will be.
What is needed therefore is a system and method of time-compressing media while minimizing the viewer-perceived discontinuity.